/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.qihoo.qsql.org.apache.calcite.rel.rules;

import com.qihoo.qsql.org.apache.calcite.plan.RelOptRule;
import com.qihoo.qsql.org.apache.calcite.plan.RelOptRuleCall;
import com.qihoo.qsql.org.apache.calcite.plan.RelOptUtil;
import com.qihoo.qsql.org.apache.calcite.rel.RelNode;
import com.qihoo.qsql.org.apache.calcite.rel.core.Join;
import com.qihoo.qsql.org.apache.calcite.rel.core.Project;
import com.qihoo.qsql.org.apache.calcite.rel.core.RelFactories;
import com.qihoo.qsql.org.apache.calcite.rel.type.RelDataTypeField;
import com.qihoo.qsql.org.apache.calcite.rex.RexCall;
import com.qihoo.qsql.org.apache.calcite.rex.RexNode;
import com.qihoo.qsql.org.apache.calcite.rex.RexOver;
import com.qihoo.qsql.org.apache.calcite.rex.RexShuttle;
import com.qihoo.qsql.org.apache.calcite.tools.RelBuilderFactory;

import java.util.ArrayList;
import java.util.List;

/**
 * Planner rule that pushes a {@link com.qihoo.qsql.org.apache.calcite.rel.core.Project}
 * past a {@link com.qihoo.qsql.org.apache.calcite.rel.core.Join}
 * by splitting the projection into a projection on top of each child of
 * the join.
 */
public class ProjectJoinTransposeRule extends RelOptRule {
  public static final ProjectJoinTransposeRule INSTANCE =
      new ProjectJoinTransposeRule(expr -> !(expr instanceof RexOver),
          RelFactories.LOGICAL_BUILDER);

  //~ Instance fields --------------------------------------------------------

  /**
   * Condition for expressions that should be preserved in the projection.
   */
  private final PushProjector.ExprCondition preserveExprCondition;

  //~ Constructors -----------------------------------------------------------

  /**
   * Creates a ProjectJoinTransposeRule with an explicit condition.
   *
   * @param preserveExprCondition Condition for expressions that should be
   *                              preserved in the projection
   */
  public ProjectJoinTransposeRule(
      PushProjector.ExprCondition preserveExprCondition,
      RelBuilderFactory relFactory) {
    super(
        operand(Project.class,
            operand(Join.class, any())),
        relFactory, null);
    this.preserveExprCondition = preserveExprCondition;
  }

  //~ Methods ----------------------------------------------------------------

  // implement RelOptRule
  public void onMatch(RelOptRuleCall call) {
    Project origProj = call.rel(0);
    final Join join = call.rel(1);

    if (!join.getJoinType().projectsRight()) {
      return; // TODO: support SemiJoin / AntiJoin
    }

    // Normalize the join condition so we don't end up misidentified expanded
    // form of IS NOT DISTINCT FROM as PushProject also visit the filter condition
    // and push down expressions.
    RexNode joinFilter = join.getCondition().accept(new RexShuttle() {
      @Override public RexNode visitCall(RexCall rexCall) {
        final RexNode node = super.visitCall(rexCall);
        if (!(node instanceof RexCall)) {
          return node;
        }
        return RelOptUtil.collapseExpandedIsNotDistinctFromExpr((RexCall) node,
            call.builder().getRexBuilder());
      }
    });

    // locate all fields referenced in the projection and join condition;
    // determine which inputs are referenced in the projection and
    // join condition; if all fields are being referenced and there are no
    // special expressions, no point in proceeding any further
    PushProjector pushProject =
        new PushProjector(
            origProj,
            joinFilter,
            join,
            preserveExprCondition,
            call.builder());
    if (pushProject.locateAllRefs()) {
      return;
    }

    // create left and right projections, projecting only those
    // fields referenced on each side
    RelNode leftProjRel =
        pushProject.createProjectRefsAndExprs(
            join.getLeft(),
            true,
            false);
    RelNode rightProjRel =
        pushProject.createProjectRefsAndExprs(
            join.getRight(),
            true,
            true);

    // convert the join condition to reference the projected columns
    RexNode newJoinFilter = null;
    int[] adjustments = pushProject.getAdjustments();
    if (joinFilter != null) {
      List<RelDataTypeField> projJoinFieldList = new ArrayList<>();
      projJoinFieldList.addAll(
          join.getSystemFieldList());
      projJoinFieldList.addAll(
          leftProjRel.getRowType().getFieldList());
      projJoinFieldList.addAll(
          rightProjRel.getRowType().getFieldList());
      newJoinFilter =
          pushProject.convertRefsAndExprs(
              joinFilter,
              projJoinFieldList,
              adjustments);
    }

    // create a new join with the projected children
    Join newJoinRel =
        join.copy(
            join.getTraitSet(),
            newJoinFilter,
            leftProjRel,
            rightProjRel,
            join.getJoinType(),
            join.isSemiJoinDone());

    // put the original project on top of the join, converting it to
    // reference the modified projection list
    RelNode topProject =
        pushProject.createNewProject(newJoinRel, adjustments);

    call.transformTo(topProject);
  }
}

// End ProjectJoinTransposeRule.java
